1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor substrate of reduced metal contamination and to a method of evaluating contamination and defects in a substrate.
2. Discussion of the Background
Generally, a semiconductor substrate serving as the base of a semiconductor part is manufactured by slicing to prescribed thickness a silicon single crystal ingot to fabricate a silicon wafer and then polishing one or both surfaces of the silicon wafer to a mirror finished surface with a mirror polishing device (for example, see Japanese Unexamined Patent Publication (KOKAI) No. 2001-102332, which is expressly incorporated herein by reference in its entirety).
An inspection method in which bright points detected on the surface of a semiconductor substrate with a foreign matter inspection device are observed has been proposed as a quality evaluation method for such wafers having a mirror finished surface. In this inspection method, particles on the substrate surface, Crystal Originated Particles (COPs), dislocations, various surface pits due to the quality of the substrate crystal, and the like are detected as bright points. Since particles on the substrate are observed as protrusions and surface pits are observed as indentations, the causes of bright points caused by particles and surface pits can be specified to an extent.
However, in wafers of which surfaces have been subjected to mirror polishing, there is a problem in that metal ions contained in the slurry used in mirror polishing diffuse into the wafer during mirror polishing, contaminating the bulk near the surface. In such metal-contaminated wafers, crystal defects and surface roughness occur on the surface, compromising quality. Thus, there is a need for a method for providing a semiconductor substrate with reduced metal contamination.
Further, since crystal defects and surface roughness caused by metal contamination of the bulk as set forth above do not appear as protrusions and indentations on the substrate surface, they are normally not detected as bright points in the inspection with foreign matter inspection devices, and run the risk of being supplied as a nondefective product.